African Swine Fever (ASF) Response

Ready Reference Guide—

ASF Zones and Areas for Feral Swine

July 2020 USDA APHIS Veterinary Services • Na�onal Preparedness and Incident Coordina�on (NPIC) 1 of 2

4700 River Road Unit 42 • Riverdale, MD 20737

Zones and Areas Feral Pigs*

* The minimum Infected Zone is 3 kilometers; however, when multiple pigs are found nearby on the landscape the Infected Zone will be adjusted to incorporate all 

pigs, which potentially can result in a larger Infected Zone.

Summary of ASF Zone and Area Designations

Zone/Area Definition

Infected Zone (IZ) Zone that immediately surrounds an Infected Premises or Infected Pig(s)

Buffer Zone (BZ) Zone that immediately surrounds an Infected Zone or a Contact Premises

Control Area (CA) Consists of an Infected Zone and a Buffer Zone

Surveillance Zone (SZ) Zone outside and along the border of a Control Area. The Surveillance Zone is part of the 

Free Area. More frequent sampling throughout the quarantine period is recommended.

Free Area (FA) Area not included in any Control Area. Includes the Surveillance Zone.

Summary of Key Response Actions

Swine Population 

Infected

State – Tribal Quarantine 

of Infected Premises

Control Area Plus 

Network Based Controls

USDA Extraordinary 

Emergency Declaration

72 hour National 

Movement Standstill

Feral Swine Only N/A Control Area 

+

Network Based Controls*

Yes Yes

*Epidemiological investigation to ensure infected feral swine are in their biological home range and have not been moved by human activity out of the Control Area. 

Domestic swine in Control Area are subject to movement control and surveillance activities.

For more information, please go to:

https://www.aphis.usda.gov/aphis/ourfocus/animalhealth/emer

gency-management/african-swine-fever/african-swine-fever

For more details on zones and premises designations, please see 

the APHIS FAD Framework: Response Strategies (Manual 2-0)

For the ASF Response Plan: The Red Book, click here.
African Swine Fever (ASF) Response 

Ready Reference Guide—

ASF Zones and Areas for Feral Swine

 July 2020 USDA APHIS Veterinary Services • Na�onal Preparedness and Incident Coordina�on (NPIC) 2 of 2

4700 River Road Unit 42 • Riverdale, MD 20737

Zones and Network Based Controls

Factors to Consider in Determining Control Area Size for ASF Minimum Size of Zones and Areas

Since an ASF outbreak in feral swine would involve more than one pig, and feral swine are 

free ranging animals, the IZ would likely be larger than the 3 kilometer minimum recommenda�on around a single index case. The ini�al IZ would encompass all ASF-posi�ve feral swine cases and expand beyond the home range size for the affected popula�on(s) of 

feral swine. Although the average range for feral pigs is approximately 1.5 to 3 square kilometers, home ranges vary widely, based on factors such as resources, climate, and habitat. Therefore, the exact size of the Control Area(s) will be determined by wildlife experts 

a�er ini�al assessment. 

Addi�onal work on feral swine contact networks indicate that disease transmission is uncommon between feral swine that are more than 2 kilometers apart. The resul�ng IZ 

would therefore extend at least 3 kilometers out in all direc�ons from the feral swine index case with adapta�ons for natural and manmade landscape features. Some regions 

also have addi�onal feral swine data available that could be used in the event of an outbreak to refine both home range es�mates and the size of the IZ.

The BZ will expand propor�onally with increases in the IZ so that it always provides a 

buffer equivalent to at least 2 kilometers surrounding the IZ. The BZ will indicate an area 

of increased ASF risk where no posi�ve feral swine have been detected. Addi�onally, 

there will be a SZ of at least 5 kilometers surrounding the BZ. These zones will be adapted 

as the incident progresses, in addi�on to changes in epidemiology.